Question

How many unpaired electrons are there in the following ions? (a) \(\mathrm{Al}^{3+}\) (b) \(\mathrm{Cl}^{-}\) (c) \(\mathrm{Sr}^{2+}\) (d) \(\mathrm{Zr}^{4+}\)

Short answer

Answer: (a) 0 unpaired electrons, (b) 0 unpaired electrons, (c) 0 unpaired electrons, and (d) 0 unpaired electrons.

Step-by-step solution

(Step 1: Determine electron configuration for Al³⁺)

First, find the atomic number of Aluminum (Al) from the periodic table, which is 13. This means a neutral Al atom has 13 electrons. For the Al³⁺ ion, three electrons are lost, leaving 10 electrons with an electron configuration of \(\mathrm{1s^2 2s^2 2p^6}\).

(Step 2: Identify unpaired electrons in Al³⁺)

Since all electrons are in completely filled orbitals (s and p orbitals), the Al³⁺ ion has 0 unpaired electrons.

(Step 3: Determine electron configuration for Cl¯)

From the periodic table, Chlorine (Cl) has an atomic number of 17. In the neutral state, Cl has 17 electrons. For the Cl¯ ion, one electron is gained, resulting in 18 electrons. The electron configuration is \(\mathrm{1s^2 2s^2 2p^6 3s^2 3p^6}\).

(Step 4: Identify unpaired electrons in Cl¯)

With 18 electrons filling up the s and p orbitals, there are no unpaired electrons in the Cl¯ ion.

(Step 5: Determine electron configuration for Sr²⁺)

Strontium (Sr) has an atomic number of 38. In the neutral state, Sr has 38 electrons. For the Sr²⁺ ion, two electrons are lost, resulting in 36 electrons. The electron configuration is \(\mathrm{1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6}\).

(Step 6: Identify unpaired electrons in Sr²⁺)

In the Sr²⁺ ion, all electrons fill up the s, p, and d orbitals with no unpaired electrons.

(Step 7: Determine electron configuration for Zr⁴⁺)

Lastly, Zirconium (Zr) has an atomic number of 40. In the neutral state, Zr has 40 electrons. For the Zr⁴⁺ ion, four electrons are lost, leaving 36 electrons. The electron configuration is \(\mathrm{1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6}\).

(Step 8: Identify unpaired electrons in Zr⁴⁺)

Just like Sr²⁺, the Zr⁴⁺ ion has an electron configuration that results in no unpaired electrons.

(Final Answer: Unpaired electrons in each ion)

In summary, (a) Al³⁺ has 0 unpaired electrons. (b) Cl¯ has 0 unpaired electrons. (c) Sr²⁺ has 0 unpaired electrons. (d) Zr⁴⁺ has 0 unpaired electrons.